JP4401567B2 - Recording device - Google Patents

Description

【００４５】
図５は、デジタルフィルタのハードウエア構成を示している。
【００４６】
図５において、５０１〜５０４および５１６〜５１９は１画素遅延させる遅延器、５０５〜５０９および５２０〜５２４は乗算器、５１０は加算器、５１５はラインメモリを夫々表す。
【００４７】
上記構成において、入力した画像データは、遅延器５０１〜５０４により１画素ずつ、順次遅延される。各遅延器入力の画素および遅延器５０４出力の画素は、夫々が乗算器５０５〜５０９によりフィルタ係数Ａ（−２，２）〜Ａ（２，２）を乗ぜられ、各乗算値が加算器５１０に入力される。
【００４８】
また、ラインメモリ５１５には１ライン前のデータが記憶されており、当該ラインメモリ出力画素は、同様に遅延器５１６〜５１９によって１画素ずつ遅延され、夫々の画素は乗算器５２０〜５２４によりフィルタ係数Ａ（−２，１）〜Ａ（２，１）を乗ぜられ、各乗算値が加算器５１０に入力される。
【００４９】
５１１は、上記５１５〜５２４で示される１ライン前の画素データ群の処理要素の全体を表している。同様に、処理要素５１２は２ライン前、処理要素５１３は３ライン前、処理要素５１４は４ライン前のデータの処理を行っており、夫々、処理要素５１１と同一構成なので、その詳細を省略する。
【００５０】
上記のように、要素５０１〜５０９および処理要素５１１〜５１３によって全２５画素に係数を乗算した結果を加算器５１０で加算することにより、フィルタとしての畳み込み演算が施される。
【００５１】
以下、補正値算出の詳細について説明する。
【００５２】
画像メモリ１１０に記憶された画像データは、図４に示したテストパターンの画像を読み取ったものである。画像メモリ１１０に蓄えられた画像は、各周波数を表す複数の黒線の組と、濃度の基準となる白パッチおよび黒パッチからなる。
【００５３】
ここで、図４を参照して詳細に説明する。図４中で、４０１は画像データもしくは紙上に印字された全体を表し、４０２は白部の基準となる白パッチを、４０３は黒部の基準となる黒パッチを表す。
【００５４】
４０４は、周波数２本／ｍｍに相当する黒と白の繰り返しパターン、４０５は、４０４と同一パターンを９０°回転したパターン、４０６は、周波数４本／ｍｍに相当する黒と白の繰り返しパターン、４０７は、４０６と同一パターンを９０°回転したパターン、４０８は、周波数６本／ｍｍに相当する黒と白の繰り返しパターン、４０９は、４０８と同一パターンを９０°回転したパターン、４１０は、周波数８本／ｍｍに相当する黒と白の繰り返しパターン、４１１は、４１０と同一パターンを９０°回転したパターンである。
【００５５】
画像領域判定回路１１１は、図４におけるパッチおよびパターン４０２〜４１１が占める夫々の領域を切り出し、補正値算出回路１１２は、夫々の領域の読み取り値からフィルタ係数を算出する。以下の説明において、便宜上、上記切り出されるパターンの占有領域を「領域」と記し、該当パターンの参照符号で表す。
【００５６】
先ず、領域４０２を読み取り、その平均値Ｗを求める。次に、領域４０３を読み取り、その平均値Ｂを求める。そして、領域４０４〜４１１については、図６に示すように、最大値と最小値を求める。
【００５７】
即ち、領域４０４の最大値Ｗ１と最小値Ｂ１、領域４０５の最大値Ｗ２と最小値Ｂ２、領域４０６の最大値Ｗ３と最小値Ｂ３、領域４０７の最大値Ｗ４と最小値Ｂ４、領域４０８の最大値Ｗ５と最小値Ｂ５、領域４０９の最大値Ｗ６と最小値Ｂ６、領域４１０の最大値Ｗ７と最小値Ｂ７、および領域４１１の最大値Ｗ８と最小値Ｂ８を夫々求め、これらの値から、各パターンの該当周波数におけるＭＴＦを求める。
【００５８】
即ち、２本／ｍｍの主走査ＭＴＦ（Ｍ２）および副走査ＭＴＦ（Ｓ２）を、式（１）および式（２）より求める。
【００５９】
Ｍ２＝（Ｗ１−Ｂ１）／（Ｗ−Ｂ） （１）
Ｓ２＝（Ｗ２−Ｂ２）／（Ｗ−Ｂ） （２）
【００６０】
以下同様に、４本／ｍｍ、６本／ｍｍ、８本／ｍｍの主走査ＭＴＦ（Ｍ４，Ｍ６，Ｍ８）および副走査ＭＴＦ（Ｓ４，Ｓ６，Ｓ８）を、式（３）〜式（８）にしたがって求める。
【００６１】
Ｍ４＝（Ｗ３−Ｂ３）／（Ｗ−Ｂ） （３）
Ｓ４＝（Ｗ４−Ｂ４）／（Ｗ−Ｂ） （４）
Ｍ６＝（Ｗ５−Ｂ５）／（Ｗ−Ｂ） （５）
Ｓ６＝（Ｗ６−Ｂ６）／（Ｗ−Ｂ） （６）
Ｍ８＝（Ｗ７−Ｂ７）／（Ｗ−Ｂ） （７）
Ｓ８＝（Ｗ８−Ｂ８）／（Ｗ−Ｂ） （８）
【００６２】
図７は、このようにして算出した各周波数におけるＭＴＦ特性を表わす特性図である。算出されたこの特性は、図８に示す補正特性を利用して補正でき、これにより所望のフィルタ係数を算出することが出来る。図８の補正特性は図７の特性を逆フーリエ変換することにより得られ、これにより各周波数のＭＴＦ特性を１００％に補正するものである。
【００６３】
なお、補正すべきターゲットは各周波数とも１００％である必要はない。原稿よりも先鋭さ（シャープネス）を強調するモード、原稿よりも平滑化気味に再現するモード等、所望のＭＴＦをターゲットとして、そのターゲットにＭＴＦを補正するようにフィルタ係数を作ることも可能である。
【００６４】
また、予めいくつかのフィルタ係数を用意しておき、計算されたＭＴＦ値に基づいていずれかのフィルタ係数を選択するような構成とすることもできる。
【００６５】
（第２実施形態）
図９は、本発明に係る第２実施形態を示すブロック図である。
【００６６】
ここに示す第２実施形態では、図２の第１実施形態における補正値算出回路１１２に代えて、リーダＭＴＦとプリンタＭＴＦを分けて記憶する記憶装置を設け、補正値算出手段もＭＴＦ算出とフィルタ係数算出に分けて設けた構成を採用した。
【００６７】
第１実施形態では、ＭＴＦ特性をリーダ部とプリンタ部で分けて記憶していなかったために、原稿台に置かれた原稿をリーダで読み取る動作を伴う複写動作とホストコンピュータ（図示せず）から送られてきたデータを印字する印字動作とではＭＴＦ特性の劣化が異なってしまう。そこで本実施形態では、リーダのＭＴＦとプリンタのＭＴＦを別々に記憶しておき、各動作に合致したフィルタ係数を算出させるために図９の構成を採用したのである。
【００６８】
なお、ホストコンピュータから送られてきた画像データはプリンタコントローラ（図示せず）により展開され、展開された画像信号に基づいて画像記録が行なわれる。
【００６９】
図９において、９０１はＭＴＦ算出回路、９０２はリーダＭＴＦ記憶装置、９０３はプリンタＭＴＦ記憶装置、９０４はフィルタ係数算出回路である。
【００７０】
先ず、本実施形態においてリーダＭＴＦを算出する場合を説明する。本実施形態では、図４に示した画像データを精密印刷したテストチャートを用意する。
【００７１】
このチャートは、印刷によるＭＴＦ劣化の無い理想的な精密印刷機で印刷されているものとする。このチャートを原稿台ガラス３０２上に乗せて、読み取りユニット３０３による走査を行なって入力センサ部１０１に画像を読み込む。
【００７２】
入力された画像データは、入力補正回路１０２により入力系のシェーディング補正が施され、画像メモリ１１０に記憶される。画像メモリ１１０に一時的に蓄えられた画像は画像領域判定回路１１１に送られる。画像領域判定回路１１１は、この画像データから各周波数を表す部分の切り出しを行ない、以降、本実施形態に特徴的な独立したリーダＭＴＦに係る処理が行なわれる。
【００７３】
すなわち、ＭＴＦ算出回路９０１は各周波数に該当するパターンのＭＴＦを判定し、その結果をリーダＭＴＦ記憶装置９０２に送る。リーダＭＴＦ記憶装置９０２はリーダＭＴＦの値を記憶する。
【００７４】
次にプリンタＭＴＦを算出する場合を説明する。
【００７５】
第１実施形態と同じように、先ず、パターン発生回路１０９により、図４を参照して説明したテストパターンを発生する。このテストパターンはＭＴＦ（Modulation Transfer Function）特性を検出するためのパターンであり、セレクタ１０３により画像信号として入力され、前述した画像処理要素のいくつかを通り（不必要な処理はスルーとなる）、プリンタ部１０８に入力される。プリンタ部１０８は、この画像データに基づいて印字を行う。
【００７６】
そしてパターンの印字が終了するとプリンタ２００より排出された用紙を原稿台ガラス３０２上に乗せて、読み取りユニット３０３の走査により入力センサ部１０１に画像を読み込む。入力された画像データは、入力補正回路１０２により入力系のシェーディング補正が施され、画像メモリ１１０に記憶される。画像メモリ１１０に一時的に蓄えられた画像は画像領域判定回路１１１に送られる。
【００７７】
画像領域判定回路１１１は、この画像データから各周波数を表す部分の切り出しを行ない、以降、本実施形態に特徴的な独立したプリンタＭＴＦに係る処理が行なわれる。
【００７８】
すなわち、ＭＴＦ算出回路９０１は各周波数に該当するパターンのＭＴＦを判定し、そのＭＴＦ特性からリーダＭＴＦ成分を除いたものを、即ち各周波数においてリーダＭＴＦで除算したものをプリンタＭＴＦとして、プリンタＭＴＦ記憶装置９０３に送る。プリンタＭＴＦ記憶装置９０３は、算出されたプリンタＭＴＦを記憶する。
【００７９】
フィルタ係数算出回路９０４は、上述のようにして記憶装置９０２および記憶装置９０３に記憶した２つのＭＴＦからフィルタ係数を算出する。つまり、プリンタＭＴＦデータを読み出してプリント時フィルタ係数を算出し、リーダＭＴＦデータとプリンタＭＴＦデータを読み出して複写時フィルタ係数を算出する。算出された、この２種類のフィルタ係数は、バックアップＲＡＭ１１３に記憶される。
【００８０】
そして、実際の複写時もしくはプリント時には、動作にマッチしたフィルタ係数がバックアップＲＡＭ１１３から読み出され、フィルタ１０７は、このフィルタ係数に基づいてフィルタ処理を施す。フィルタ１０７によるＭＴＦのデジタル的な補正によって、原稿をリーダで読み取る複写動作とホストコンピュータ（図示せず）からのデータを印字する印字動作とでＭＴＦ特性を合致させた、プロセス条件の変化や固体差によるＭＴＦ劣化を良好に補正した高品位な画像を得ることができる。
【００８１】
（第３実施形態）
図１０は、本発明に係る第３実施形態を示すブロック図である。
【００８２】
ここに示す第３実施形態では、図９の第２実施形態における画像メモリ１１０に代えて、パターン発生回路１００９に接続したネットワークＩ／Ｆ１０１０を設けた構成を採用した。ネットワークＩ／Ｆ１０１０はネットワークケーブル１０１５に繋がっており、このネットワークケーブル１０１５に接続されている他の装置との通信を可能とする。
【００８３】
例えば、本実施形態の記録装置と離れた場所にあるＭＦＰ（Multi Function Printer）１０１４と、ネットワークケーブル１０１５を介して通信する場合について考える。本実施形態装置の原稿読取装置３００で読み込んだ画像を２値化してＭＦＰ１０１４に送信し、この画像をＭＦＰ１０１４によってプリントする、所謂ネットワークプリンティングを行なうに際しては、プリント実行前にネットワーク上で以下の補正動作を行わせる。なお、ＭＦＰ１０１４はスキャナ部とプリンタ部を備えた多機能複写機であるが、ＭＴＦ補正機能は備えていないものとする。
【００８４】
先ず、パターン発生回路１００９によって図４に示したようなパターンを発生させる。そして、ネットワークＩ／Ｆ１０１０は、そのパターンをパターン発生回路１００９から受け取って、ネットワークケーブル１０１５を通じてＭＦＰ１０１４に送信する。ＭＦＰ１０１４は、そのパターンを紙等にプリント出力する。
【００８５】
次に、このようにしてＭＦＰ１０１４により出力されたパターン、または第２実施形態で用いた精密印刷されたチャートをＭＦＰ１０１４のスキャナ部で読み取り、その画像読取データをＭＦＰ１０１４からネットワークＩ／Ｆ１０１０へ、ネットワークケーブル１０１５を通じて送信する。
【００８６】
そして、本実施形態装置側で、ＭＦＰ１０１４から送られてきた画像データに基づいて第２実施形態と同一のアルゴリズムを用いてフィルタ係数の補正を行うことにより、ネットワークを通じてＭＴＦ補正機能の無いＭＦＰ１０１４によりプリントする場合、或いはＭＦＰ１０１４によりスキャンさせて画像を取り込む場合においても、夫々のリーダＭＴＦ、プリンタＭＴＦからフィルタ係数を算出し、フィルタ処理を施すことにより、プロセス条件の変化や固体差によるＭＴＦ劣化を良好に補正した良好な画像をネットワーク上で得ることが出来る。
【００８７】
（他の実施形態）
上記実施形態の他に、第１実施形態と第３実施形態を組み合わせた構成、つまり、第１実施形態における画像メモリに代えてパターン発生回路に接続したネットワークＩ／Ｆを設けた構成を実施することもできる。
【００８８】
【発明の効果】
以上説明したように本発明に係る記録装置によれば、読み取り手段及び記録手段のＭＴＦ特性を判定し、それらを組み合わせてフィルタ係数を算出し、この係数を用いてデジタルフィルタによるフィルタ処理を施すことにより、記録手段のプロセス条件の変化や固体差によるＭＴＦ劣化を良好に補正することが出来、また、ネットワークを介してつながっている他の記録装置等に対しても、それぞれの特性に応じたＭＴＦ補正、すなわち、個体差を考慮した補正を行うことが出来るため、記録品位を向上させることが可能となる。
【図面の簡単な説明】
【図１】本発明に係る第１実施形態の記録装置を示した内部構成図である。
【図２】本発明に係る第１実施形態の記録装置を示したブロック図である。
【図３】フィルタ係数の詳細を示した説明図である。
【図４】ＭＴＦ判定用のパターンデータ及び印刷されたチャートの詳細を表す平面図である。
【図５】デジタルフィルタのハードウエア構成図である。
【図６】読み取ったデータの最大値、最小値を説明する説明図である。
【図７】各周波数におけるＭＴＦ特性を示した特性図である。
【図８】ＭＴＦ特性を補正するための特性を示した特性図である。
【図９】本発明に係る第２実施形態の記録装置を示したブロック図である。
【図１０】本発明に係る第３実施形態の記録装置を示したブロック図である。
【符号の説明】
１０１ 入力センサ部
１０２ 入力補正回路
１０３ セレクタ
１０７ フィルタ
１０８ プリンタ部
１０９ パターン発生回路
１１０ 画像メモリ
１１１ 画像領域判定回路
１１２ 補正値算出回路
１１３，１１４ バックアップＲＡＭ
２００ プリンタ
２０１ カセット
２０２ ピックアップローラ
２０３，２０５ レジローラ
２０４ ガイド板
２０６ 搬送ベルト
２０７ プラテン
２０８ 定着器
２０９ 排紙ガイド
２１０ 排紙ローラ
２１１ 排紙トレイ
２１２ａ アレイ
２１３ａ 現像器
２１４ａ ドラム
３００ 原稿読取装置
３０１ 原稿圧板
３０２ 原稿台ガラス
３０３ ユニット
３０４ 拡散板
３０５，３０８，３０９ ミラー
３０６ 照明ランプ
３０７ ミラーユニット
３１０ レンズ
５０１，５１６ 遅延器
５０５，５２０ 乗算器
５１０ 加算器
５１５ ラインメモリ
９０１ 算出回路
９０２，９０３ 記憶装置
９０４ フィルタ係数算出回路
１００９ パターン発生回路
１０１０ ネットワークＩ／Ｆ
１０１５ ネットワークケーブル[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording apparatus, and more particularly, a recording apparatus that includes a digital filter and corrects MTF degradation by image input / output, and corrects MTF degradation by image input / output between recording apparatuses connected to a network. The present invention relates to a recording apparatus.
[0002]
[Prior art]
As this type of apparatus, an electrophotographic recording apparatus is generally known.
[0003]
In such a recording apparatus, the reading unit is provided with a photoelectric conversion element such as a CCD, for example, and the image on the document is converted into an electrical signal by scanning the photoelectric conversion element relative to the document. Then, a latent image is formed on the photosensitive drum by driving a laser light source or an LED based on the electric signal obtained by the reading. A toner is attached to a portion where a potential difference is generated by the latent image and developed, and the visualized image is transferred onto a recording medium such as a recording paper and reproduced.
[0004]
[Problems to be solved by the invention]
In such an electrophotographic recording apparatus, process conditions may change due to environmental conditions, changes with time, material deterioration, and the like. Due to such a change in process conditions, there arises a problem that the MTF (Modulation Transfer Function) of the image deteriorates when the read image is reproduced on paper. This deterioration varies depending on the electrophotographic apparatus, and may change with time.
[0005]
Further, when printing or scanning via a network, there is a problem that a good image cannot be obtained if data is exchanged between devices having different MTF characteristics.
[0006]
The present invention has been made on the basis of the above-mentioned viewpoint, and the object is to set an optimum filter coefficient and perform good MTF correction to improve the recording quality even when the MTF characteristic changes. It is an object of the present invention to provide a recording apparatus that can perform the above-described operation.
[0007]
[Means for Solving the Problems]
One aspect of the present invention made to solve the above problems is a recording apparatus connected to another recording apparatus via a network, wherein the image reading means Or host device An image processing means for performing predetermined image processing on the image signal obtained by the above, a recording means for recording an image corresponding to the image signal processed by the image processing means on a recording material, and a test pattern including a plurality of types of patterns Test pattern generating means for generating a test pattern corresponding to an image signal having a different frequency for each pattern, and means for transmitting and receiving image signals to and from the other recording apparatus having other image reading means and other recording means The test pattern is transmitted to the other recording device, and the other image reading means is A read signal obtained by reading a test chart on which a predetermined pattern is printed Communication means for receiving a read signal obtained by reading the test pattern printed on the recording material using the other recording means, and the other based on the received signal Record means Frequency characteristics And the other Image reading The frequency characteristics of the means Independently Detecting means for detecting, and by the detecting means R detection From the respective frequency characteristics of the other recording means and the other image reading means Calculating means for calculating a filter coefficient used in the digital filter means included in the image processing means, When recording by other recording means and when reading by the other image reading means, the calculated filter coefficient is used. Said each A band pass characteristic filtering process is performed to correct the frequency characteristic.
[0009]
the above State of The test pattern generation means generates a plurality of repetitive patterns having different repetition frequencies in the main scanning direction of the image reading means and a plurality of repetitive patterns having different repetition frequencies in the sub-scanning direction of the image reading means. Can do. In the latter embodiment, the test chart is other A plurality of repetitive patterns having different repetitive frequencies in the main scanning direction of the image reading means; other A plurality of repetitive patterns having different repetitive frequencies in the sub-scanning direction of the image reading means may be printed in advance.
[0011]
The present invention Another Is a recording apparatus connected to another recording apparatus via a network, the image processing means for performing predetermined image processing on the image signal obtained by the image reading means or the host device, and the image processing means A test chart in which a recording unit for recording an image corresponding to the processed image signal on a recording material and another image reading unit provided in the other recording apparatus are printed with a predetermined pattern in advance. Read signal read And receiving means for receiving a read signal obtained by reading a test pattern printed on a recording material using other recording means provided in the recording apparatus, and the other based on the received signal. Record means Frequency characteristics And the other Image reading Detecting means for independently detecting the frequency characteristics of the means; and R detection From the respective frequency characteristics of the other recording means and the other image reading means Calculating means for calculating a filter coefficient used in the digital filter means included in the image processing means, When recording by other recording means and when reading by the other image reading means, the calculated filter coefficient is used. Said each A band pass characteristic filtering process is performed to correct the frequency characteristic.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is an internal configuration diagram of a recording apparatus capable of image copying showing a first embodiment according to the present invention.
[0023]
The document reading apparatus 300 illuminates the document placed on the document table glass 302 with light from the illumination lamp 306 and light diffused by the diffusion plate 304, and reflects the reflected light through mirrors 305, 308, and 309. Then, an image is formed on the CCD 311 through the lens 310, and this image is photoelectrically converted to obtain an image signal.
[0024]
The CCD 311 of this embodiment is composed of three rows of R (red), G (green), and B (blue) in which 7200 pixels are arranged from the front to the back in the drawing. The reading unit 303 on which the diffusing plate 304, the mirror 305, and the illumination lamp 306 are mounted moves to the left and right in the drawing on a rail (not shown), and the mirror unit 307 on which the mirrors 308 and 309 are mounted also moves in synchronization therewith. . By moving these two units to the left and right, the entire document can be read. The document pressure plate 301 is for pressing the document against the document table glass 302.
[0025]
Next, the image signal is subjected to image processing described later, and then sent to the printer 200.
[0026]
In the printer 200, the paper is drawn out by a pickup roller 202 from a cassette 201 that stores paper as a recording material. The paper passes through the first registration roller 203, the guide plate 204, and the second registration roller 205, and is adsorbed onto the conveyance belt 206.
[0027]
On the other hand, the image signal is separated into four colors CMYK. Among them, the C (cyan) signal is converted into an optical signal by the LED array 212a and recorded as a latent image on the drum 214a. The latent image on the drum 214a is developed by the developing device 213a, and toner is deposited on the drum 214a. The developed toner image is transferred onto paper on the platen 207. The image forming process described above is a well-known electrophotographic process.
[0028]
Similarly, the remaining M (magenta), Y (yellow), and K (black) are similarly image-formed by a well-known electrophotographic process using a set of LED array, drum, and developer, and the toner image is transferred to the paper. The The toner transferred onto the paper is heated and fixed on the paper by the fixing device 208. The paper that has been fixed is discharged to the paper discharge tray 211 via the paper discharge guide 209 and the paper discharge roller 210.
[0029]
FIG. 2 is a block diagram showing a first embodiment according to the present invention.
[0030]
In FIG. 2, an input sensor unit 101 includes a photoelectric conversion element such as a CCD and a driving device that moves the photoelectric conversion element for scanning, thereby reading and scanning a document. Document image data read by the input sensor unit 101 is sequentially sent to the input correction circuit 102. Here, quantization for converting each pixel image data into digital data is performed, and shading correction for correcting unevenness in sensitivity of the CCD sensor and unevenness in illuminance by the illumination light source is performed by digital arithmetic processing.
[0031]
The selector 103 selects either input image data or a test pattern described later and sends it to the subsequent image processing circuit. The LOG conversion circuit 104 converts RGB image (luminance) data into CMY density data using a lookup table. A black extraction circuit 105 performs black extraction. A masking circuit 106 performs a masking process corresponding to the color development characteristics of the printing toner (or ink).
[0032]
Reference numeral 107 denotes a digital filter that performs a convolution operation with neighboring pixels and applies an effect such as smoothing or edge enhancement to the image. This digital filter will be described later. A printer unit 108 performs printing based on the image data sent from the filter 107. Reference numeral 109 denotes a pattern generation circuit that generates a test pattern.
[0033]
An image memory 110 stores read image information. Reference numeral 111 denotes an image area determination circuit that determines a printed area from the read image. A correction value calculation circuit 112 calculates a filter coefficient from the read image. Reference numeral 113 denotes a backup RAM.
[0034]
A case where filter coefficients are calculated in the above configuration will be described.
[0035]
First, the pattern generation circuit 109 generates a test pattern, which will be described in detail later with reference to FIG. This test pattern is a pattern for detecting an MTF (Modulation Transfer Function) characteristic, which is input as an image signal by the selector 103, passes through some of the image processing elements described above (unnecessary processing is through), The data is input to the printer unit 108. The printer unit 108 performs printing based on the image data.
[0036]
When the pattern printing is completed, the paper discharged from the printer 200 is placed on the platen glass 302 and the image is read into the input sensor unit 101 by scanning of the reading unit 303. The input image data is subjected to input shading correction by the input correction circuit 102 and stored in the image memory 110. The image temporarily stored in the image memory 110 is sent to the image area determination circuit 111.
[0037]
The image area determination circuit 111 cuts out a portion representing each frequency from the image data. The correction value calculation circuit 112 determines the MTF of the pattern corresponding to each frequency, and calculates a predetermined filter coefficient. This filter coefficient represents what frequency characteristic the digital filter has. Details of the image area determination and correction value calculation will be described later. The calculated filter coefficient is stored in the backup RAM 113.
[0038]
Then, during normal image copying, the MTF of the image is digitally corrected by the filter 107 based on the filter coefficient data stored in the backup RAM 114, thereby eliminating the MTF deterioration that occurs in the reader and the printer. It is possible to obtain a high-quality image in which MTF deterioration due to a change in conditions and a difference between solids is well corrected.
[0039]
Next, details of the digital filter will be described.
[0040]
This digital filter is configured in two dimensions, and in the present embodiment, a 5 × 5 size filter will be described as an example. The filter size is not limited to 5 × 5, and may be 9 × 9, 7 × 7, or the like. Of course, it may be larger than that, or may have a different size (for example, 9 × 7) in the main scanning direction and the sub-scanning direction.
[0041]
FIG. 3 shows a functional configuration of the digital filter.
[0042]
FIG. 3 shows how the coefficients of the digital filter are entered. The digital filter shown here performs a convolution operation of 25 pixels including the pixel of interest (i, j).
[0043]
When each coefficient is represented by An, m and the value of each pixel is S (i, j), the output result F (i, j) subjected to the filter operation is represented by the following expression.
[0044]
[Expression 1]

[0045]
FIG. 5 shows the hardware configuration of the digital filter.
[0046]
In FIG. 5, reference numerals 501 to 504 and 516 to 519 denote delay units that delay one pixel, 505 to 509 and 520 to 524 denote multipliers, 510 denotes an adder, and 515 denotes a line memory.
[0047]
In the above configuration, the input image data is sequentially delayed pixel by pixel by the delay units 501 to 504. The pixels at the input of each delay device and the pixels at the output of the delay device 504 are multiplied by filter coefficients A (−2, 2) to A (2, 2) by multipliers 505 to 509, respectively, and each multiplication value is added to the adder 510. Is input.
[0048]
The line memory 515 stores data one line before. Similarly, the line memory output pixels are delayed one by one by delay units 516 to 519, and each pixel is filtered by multipliers 520 to 524. Multiplied by coefficients A (−2, 1) to A (2, 1), and each multiplied value is input to adder 510.
[0049]
Reference numeral 511 denotes the entire processing element of the pixel data group one line before indicated by 515 to 524. Similarly, the processing element 512 processes data two lines before, the processing element 513 processes three lines before, and the processing element 514 processes data four lines before, and the details are omitted because they have the same configuration as the processing element 511. .
[0050]
As described above, the result of multiplying all the 25 pixels by the coefficients by the elements 501 to 509 and the processing elements 511 to 513 is added by the adder 510 to perform a convolution operation as a filter.
[0051]
Details of the correction value calculation will be described below.
[0052]
The image data stored in the image memory 110 is obtained by reading the test pattern image shown in FIG. The image stored in the image memory 110 includes a set of a plurality of black lines representing each frequency, and a white patch and a black patch that serve as a density reference.
[0053]
Here, it demonstrates in detail with reference to FIG. In FIG. 4, 401 represents image data or the whole printed on paper, 402 represents a white patch serving as a reference for white portions, and 403 represents a black patch serving as a reference for black portions.
[0054]
404 is a black and white repetitive pattern corresponding to a frequency of 2 lines / mm, 405 is a pattern obtained by rotating the same pattern as that of 90 ° by 90 °, 406 is a black and white repetitive pattern corresponding to a frequency of 4 lines / mm, 407 is a pattern obtained by rotating the same pattern as 406 by 90 °, 408 is a black and white repeating pattern corresponding to a frequency of 6 lines / mm, 409 is a pattern obtained by rotating the same pattern as 408 by 90 °, and 410 is a frequency. A black and white repetitive pattern corresponding to 8 lines / mm, 411 is a pattern obtained by rotating the same pattern as 410 by 90 °.
[0055]
The image area determination circuit 111 cuts out each area occupied by the patches and patterns 402 to 411 in FIG. 4, and the correction value calculation circuit 112 calculates a filter coefficient from the read value of each area. In the following description, for the sake of convenience, the occupied area of the pattern to be cut out is referred to as “area” and is represented by a reference numeral of the corresponding pattern.
[0056]
First, the area 402 is read and the average value W is obtained. Next, the area 403 is read and the average value B is obtained. And about the area | regions 404-411, as shown in FIG. 6, the maximum value and the minimum value are calculated | required.
[0057]
That is, the maximum value W1 and minimum value B1 of the region 404, the maximum value W2 and minimum value B2 of the region 405, the maximum value W3 and minimum value B3 of the region 406, the maximum value W4 and minimum value B4 of the region 407, and the maximum of the region 408 A value W5 and a minimum value B5, a maximum value W6 and a minimum value B6 of the region 409, a maximum value W7 and a minimum value B7 of the region 410, and a maximum value W8 and a minimum value B8 of the region 411 are obtained, and from these values, The MTF at the corresponding frequency of the pattern is obtained.
[0058]
That is, the main scanning MTF (M2) and the sub-scanning MTF (S2) of 2 lines / mm are obtained from the equations (1) and (2).
[0059]
M2 = (W1-B1) / (WB) (1)
S2 = (W2-B2) / (W-B) (2)
[0060]
Similarly, the main scanning MTFs (M4, M6, M8) and the sub-scanning MTFs (S4, S6, S8) of 4 lines / mm, 6 lines / mm, and 8 lines / mm are expressed by equations (3) to (8). )
[0061]
M4 = (W3-B3) / (W-B) (3)
S4 = (W4-B4) / (W-B) (4)
M6 = (W5-B5) / (W-B) (5)
S6 = (W6-B6) / (W-B) (6)
M8 = (W7−B7) / (W−B) (7)
S8 = (W8−B8) / (W−B) (8)
[0062]
FIG. 7 is a characteristic diagram showing the MTF characteristic at each frequency calculated as described above. This calculated characteristic can be corrected by using the correction characteristic shown in FIG. 8, and thereby a desired filter coefficient can be calculated. The correction characteristic shown in FIG. 8 is obtained by performing inverse Fourier transform on the characteristic shown in FIG. 7, thereby correcting the MTF characteristic of each frequency to 100%.
[0063]
Note that the target to be corrected need not be 100% for each frequency. It is also possible to create a filter coefficient so that the target MTF is targeted and the target MTF is corrected, such as a mode that emphasizes sharpness (sharpness) than the original and a mode that reproduces more smoothly than the original. .
[0064]
Alternatively, a configuration may be adopted in which some filter coefficients are prepared in advance and any one of the filter coefficients is selected based on the calculated MTF value.
[0065]
(Second Embodiment)
FIG. 9 is a block diagram showing a second embodiment according to the present invention.
[0066]
In the second embodiment shown here, in place of the correction value calculation circuit 112 in the first embodiment of FIG. 2, a storage device for storing the reader MTF and the printer MTF separately is provided, and the correction value calculation means also uses the MTF calculation and filter. A configuration provided separately for coefficient calculation was adopted.
[0067]
In the first embodiment, since the MTF characteristics are not separately stored in the reader unit and the printer unit, the copying operation involving the operation of reading the document placed on the document table by the reader and the transmission from the host computer (not shown). Deterioration of the MTF characteristics is different from the printing operation for printing the received data. Therefore, in the present embodiment, the configuration shown in FIG. 9 is adopted in order to store the MTF of the reader and the MTF of the printer separately and calculate the filter coefficients that match each operation.
[0068]
Image data sent from the host computer is developed by a printer controller (not shown), and image recording is performed based on the developed image signal.
[0069]
In FIG. 9, reference numeral 901 denotes an MTF calculation circuit, 902 denotes a reader MTF storage device, 903 denotes a printer MTF storage device, and 904 denotes a filter coefficient calculation circuit.
[0070]
First, a case where the reader MTF is calculated in the present embodiment will be described. In this embodiment, a test chart is prepared by precisely printing the image data shown in FIG.
[0071]
It is assumed that this chart is printed by an ideal precision printing machine with no MTF deterioration due to printing. This chart is placed on the platen glass 302 and scanned by the reading unit 303 to read an image into the input sensor unit 101.
[0072]
The input image data is subjected to input shading correction by the input correction circuit 102 and stored in the image memory 110. The image temporarily stored in the image memory 110 is sent to the image area determination circuit 111. The image area determination circuit 111 cuts out a portion representing each frequency from the image data, and thereafter, processing related to the independent reader MTF characteristic of the present embodiment is performed.
[0073]
That is, the MTF calculation circuit 901 determines the MTF of the pattern corresponding to each frequency and sends the result to the reader MTF storage device 902. The reader MTF storage device 902 stores the value of the reader MTF.
[0074]
Next, a case where the printer MTF is calculated will be described.
[0075]
As in the first embodiment, first, the pattern generation circuit 109 generates the test pattern described with reference to FIG. This test pattern is a pattern for detecting an MTF (Modulation Transfer Function) characteristic, which is input as an image signal by the selector 103, passes through some of the image processing elements described above (unnecessary processing is through), The data is input to the printer unit 108. The printer unit 108 performs printing based on the image data.
[0076]
When the pattern printing is completed, the paper discharged from the printer 200 is placed on the platen glass 302 and the image is read into the input sensor unit 101 by scanning of the reading unit 303. The input image data is subjected to input shading correction by the input correction circuit 102 and stored in the image memory 110. The image temporarily stored in the image memory 110 is sent to the image area determination circuit 111.
[0077]
The image area determination circuit 111 cuts out a portion representing each frequency from the image data, and thereafter, processing related to an independent printer MTF characteristic of the present embodiment is performed.
[0078]
That is, the MTF calculation circuit 901 determines the MTF of the pattern corresponding to each frequency, and stores the printer MTF as the printer MTF obtained by dividing the MTF characteristic by removing the reader MTF component, that is, the frequency divided by the reader MTF at each frequency. Send to device 903. The printer MTF storage device 903 stores the calculated printer MTF.
[0079]
The filter coefficient calculation circuit 904 calculates a filter coefficient from the two MTFs stored in the storage device 902 and the storage device 903 as described above. That is, the printer MTF data is read to calculate the filter coefficient at the time of printing, and the reader MTF data and the printer MTF data are read to calculate the filter coefficient at the time of copying. The calculated two types of filter coefficients are stored in the backup RAM 113.
[0080]
Then, at the time of actual copying or printing, the filter coefficient matching the operation is read from the backup RAM 113, and the filter 107 performs a filter process based on this filter coefficient. Due to the digital correction of the MTF by the filter 107, the MTF characteristics are matched between the copying operation for reading an original with a reader and the printing operation for printing data from a host computer (not shown). It is possible to obtain a high-quality image in which the MTF deterioration due to is corrected well.
[0081]
(Third embodiment)
FIG. 10 is a block diagram showing a third embodiment according to the present invention.
[0082]
In the third embodiment shown here, a configuration in which a network I / F 1010 connected to the pattern generation circuit 1009 is provided in place of the image memory 110 in the second embodiment of FIG. A network I / F 1010 is connected to a network cable 1015 and enables communication with other devices connected to the network cable 1015.
[0083]
For example, consider a case where communication is performed via a network cable 1015 with an MFP (Multi Function Printer) 1014 located at a remote location from the recording apparatus of the present embodiment. When performing so-called network printing in which an image read by the document reading apparatus 300 of the present embodiment is binarized and transmitted to the MFP 1014 and this image is printed by the MFP 1014, the following correction operation is performed on the network before printing. To do. Note that the MFP 1014 is a multi-function copier that includes a scanner unit and a printer unit, but does not include an MTF correction function.
[0084]
First, the pattern generation circuit 1009 generates a pattern as shown in FIG. The network I / F 1010 receives the pattern from the pattern generation circuit 1009 and transmits it to the MFP 1014 through the network cable 1015. The MFP 1014 prints out the pattern on paper or the like.
[0085]
Next, the pattern output by the MFP 1014 or the precisely printed chart used in the second embodiment is read by the scanner unit of the MFP 1014, and the image reading data is transferred from the MFP 1014 to the network I / F 1010 to the network cable. 1015 is transmitted.
[0086]
Then, the apparatus according to the present exemplary embodiment performs the correction of the filter coefficient using the same algorithm as that of the second exemplary embodiment on the basis of the image data transmitted from the MFP 1014, so that the MFP 1014 having no MTF correction function can print over the network. Even when scanning is performed by the MFP 1014 or an image is captured, the filter coefficient is calculated from each reader MTF and printer MTF, and the filter processing is performed, so that the MTF deterioration due to changes in process conditions and individual differences is improved. A corrected good image can be obtained on the network.
[0087]
(Other embodiments)
In addition to the above-described embodiment, a configuration in which the first embodiment and the third embodiment are combined, that is, a configuration in which a network I / F connected to the pattern generation circuit is provided instead of the image memory in the first embodiment is implemented. You can also.
[0088]
【The invention's effect】
As described above, according to the recording apparatus of the present invention, the MTF characteristics of the reading unit and the recording unit are determined, a filter coefficient is calculated by combining them, and a filter process using a digital filter is performed using this coefficient. Therefore, it is possible to satisfactorily correct MTF degradation due to changes in the process conditions of the recording means and individual differences, and also to other recording devices connected via a network, the MTF corresponding to each characteristic. Since the correction, that is, the correction considering individual differences can be performed, the recording quality can be improved.
[Brief description of the drawings]
FIG. 1 is an internal configuration diagram illustrating a recording apparatus according to a first embodiment of the invention.
FIG. 2 is a block diagram showing the recording apparatus of the first embodiment according to the present invention.
FIG. 3 is an explanatory diagram showing details of filter coefficients.
FIG. 4 is a plan view showing details of pattern data for MTF determination and a printed chart.
FIG. 5 is a hardware configuration diagram of a digital filter.
FIG. 6 is an explanatory diagram for explaining a maximum value and a minimum value of read data.
FIG. 7 is a characteristic diagram showing MTF characteristics at each frequency.
FIG. 8 is a characteristic diagram showing characteristics for correcting MTF characteristics.
FIG. 9 is a block diagram illustrating a recording apparatus according to a second embodiment of the invention.
FIG. 10 is a block diagram illustrating a recording apparatus according to a third embodiment of the invention.
[Explanation of symbols]
101 Input sensor section
102 Input correction circuit
103 selector
107 Filter
108 Printer
109 Pattern generation circuit
110 Image memory
111 Image Area Determination Circuit
112 Correction value calculation circuit
113,114 Backup RAM
200 printer
201 cassette
202 Pickup roller
203, 205 cashier roller
204 Guide plate
206 Conveyor belt
207 Platen
208 Fixer
209 Paper ejection guide
210 Paper discharge roller
211 Output tray
212a array
213a Developer
214a drum
300 Document reader
301 Document platen
302 Platen glass
303 units
304 Diffuser
305, 308, 309 mirror
306 Lighting lamp
307 mirror unit
310 lens
501 and 516 delay units
505, 520 multiplier
510 adder
515 line memory
901 Calculation circuit
902, 903 storage device
904 Filter coefficient calculation circuit
1009 Pattern generation circuit
1010 Network I / F
1015 Network cable

Claims (4)

A recording device connected to another recording device via a network,
Image processing means for performing predetermined image processing on an image signal obtained by an image reading means or a host device;
Recording means for recording an image corresponding to the image signal processed by the image processing means on a recording material;
Test pattern generating means for generating a test pattern corresponding to an image signal having a different frequency, which is a test pattern including a plurality of types of patterns,
A means for transmitting and receiving an image signal to and from the other recording apparatus having other image reading means and other recording means, wherein the test pattern is transmitted to the other recording apparatus, and the other image reading means communication means for receiving a read signal obtained by reading said test pattern is printed on a recording medium by using a read signal and the other recording means by reading a pre-test chart on which a predetermined pattern is printed,
Detecting means for independently detecting the frequency characteristics of the other recording means and the frequency characteristics of the other image reading means based on the received signal;
From each frequency characteristic of the detection the other recording means and said other image reading means detected Ri by the unit, and a calculating means for calculating the filter coefficients used in the digital filter means having said image processing means,
When recording by the other recording means and when reading by the other image reading means , the filter processing of the band pass characteristic is performed so as to correct each frequency characteristic using the calculated filter coefficient. A recording apparatus. The recording apparatus according to claim 1,
The test pattern generation means generates a plurality of repetitive patterns having different repetition frequencies in the main scanning direction of the image reading means and a plurality of repetitive patterns having different repetition frequencies in the sub-scanning direction of the image reading means. Recording device. The recording apparatus according to claim 1,
The test chart, and the other image reading means in the main scanning direction is repeated a plurality of repetitive patterns of different frequencies, a plurality of repetitive patterns repetition frequency in the sub-scanning direction different from the other image reading means is preprinted A recording apparatus. A recording device connected to another recording device via a network,
Image processing means for performing predetermined image processing on an image signal obtained by an image reading means or a host device;
Recording means for recording an image corresponding to the image signal processed by the image processing means on a recording material;
Other image reading means provided in the other recording apparatus prints on a recording material using a read signal obtained by reading a test chart on which a predetermined pattern is printed in advance and the other recording means provided in the recording apparatus. Receiving means for receiving a read signal obtained by reading the test pattern,
Detecting means for independently detecting the frequency characteristics of the other recording means and the frequency characteristics of the other image reading means based on the received signal;
From each frequency characteristic of the detection the other recording means and said other image reading means detected Ri by the unit, and a calculating means for calculating the filter coefficients used in the digital filter means having said image processing means,
When recording by the other recording means and when reading by the other image reading means , the filter processing of the band pass characteristic is performed so as to correct each frequency characteristic using the calculated filter coefficient. A recording apparatus.

Images